1. Field of the Invention
The present invention generally relates to cased telescoped ammunition and, more particularly, is concerned with features augmenting cartridge case dimensional recovery brought about by a case skin tube of the ammunition round.
2. Description of the Prior Art
Cased telescoped ammunition is generally well-known. Representative prior art versions of such ammunition are disclosed in U.S. Pat. Nos. to Meyer et al (2,866,412), Kunz (2,996,988), LaFever et al (4,197,801), Smith (4,220,089), Bains (4,335,657) and Clarke et al (4,604,954).
Typically, a round of cased telescoped ammunition includes an elongated cylindrical case defining a chamber that contains a propellant charge. The propellant charge has an axial bore through which extends a center sleeve in coaxial relation with the case and fastened at its opposite ends to the opposite ends of the case. A telescoped projectile is housed within a forward portion of the center sleeve, whereas an aft portion of the center sleeve, referred to as a control tube, receives a piston or spud on the aft end of the projectile. A primer is positioned within the control tube aft of the projectile spud, and a small amount of propellant is contained therein between the primer and the spud.
The round of ammunition is loaded in a gun chamber located rearwardly of the gun barrel. When the round is fired, the primer ignites the small amount of propellant in the control tube. The resulting gas applies a force against the spud, driving the projectile forwardly out of the center sleeve and into the gun barrel. Next, the hot gas ignites the main propellant charge surrounding the projectile. Burning of the propellant charge produces gas at much higher pressure which drives the projectile through the gun barrel to exit the muzzle at high velocity.
The increasing pressure created by the burning propellant charge expands the ammunition case axially and radially. Expansion of the case is constrained by the opposite ends and cylindrical interior surface of the gun chamber housing the ammunition round. The pressure also acts to elastically deform the gun, enlarging the chamber. Then, when the pressure is relieved by exit of the projectile from the gun barrel, the gun chamber reverts to its unpressurized dimensions. In order to extract the case from the gun chamber, it is necessary that the case return or recover at least to dimensions which allow clearance between it and the ends and interior surface of the chamber.
Because elastic deformations of typical guns using cased telescoped ammunition are so large, special steps are required to attain the cartridge case springback required. In a typical round currently available, one step taken is to split longitudinally the skin tube of the cartridge case to relieve any pressure between the yielded skin tube and the recovered chamber diameter. The end caps are free to move relative to the split skin tube and require special measures to maintain some connection between the end caps and split skin tube. The special measures required to connect the end caps and tube skin make for unreliable cartridge case integrity, particularly after firing. Also, splitting of the skin tube allows undesirable blackening of the gun chamber to occur during firing of the round.
Therefore, a need still exists for a different approach to achievement of dimensional recovery of a cased telescoped ammunition round.